Electrochemical investigation of erosion-corrosion behavior of 6061 aluminum alloy in marine environment

The liquid-solid erosion-corrosion behavior of aluminum in artificial seawater medium at open circuit has been investigated using a submerged jet impingement rig. The aluminum alloy 6061 coupons subjected to erosion corrosion condition were placed normal to the impinging jet. The gap maintained between the nozzle and the specimen was 5mm. In the present study, sea sand was used as an erodent. Erosion corrosion rate was measured using potentiodynamic polarization and electrochemical impedance spectroscopy methods. At a flowrate of 4 lpm passivation was observed in the potentiodynamic polarization plot which was confirmed by the appearance of inductive loop in the Nyquist plot. At higher flowrates no such condition was observed. The system response to impedance studies was characterized by a high frequency capacitive loop and a capacitive loop at the lower frequency. Surface morphology was studied with scanning electron microscopy (semi quantitative analysis) and atomic force microscopy techniques. Elemental mapping was done with electron dispersive X-ray studies. The erosion-corrosion rate increased with increase in the flow rate and temperature. The results of this work will aid in the selection of material for controlled or reduced material loss in sea water circulating equipment’ and pipelines.